Numerous methods and materials exist for the construction of retaining walls. Such methods include the use of natural stone, poured in-place concrete, pre-cast concrete, masonry, and landscape timbers or railroad ties. In recent years, segmental concrete retaining wall units which are dry stacked (i.e., built without the use of mortar) have become a widely accepted product for the construction of retaining walls. Examples of such products are described in U.S. Pat. No. Re. 34,314 (Forsberg '314) and U.S. Pat. No. 5,294,216 (Sievert). Such products have gained popularity because they are mass produced, and thus relatively inexpensive. They are structurally sound, easy and relatively inexpensive to install, and couple the durability of concrete with the attractiveness of various architectural finishes.
The retaining wall system described in Forsberg '314 has been particularly successful because of its use of block design that includes, among other design elements, a unique pinning system that interlocks and aligns the retaining wall units, allowing structural strength and efficient rates of installation. This system has also shown considerable advantages in the construction of larger walls when combined with the use of geogrid tie-backs hooked over the pins, as described in U.S. Pat. No. 4,914,876 (Forsberg).
The construction of modular concrete retaining walls as described in Forsberg involves several relatively simple steps. First, a leveling pad of dense base material or unreinforced concrete is placed, compacted and leveled. Second, the initial course of blocks is placed and leveled. Two pins are placed in each block into the pin holes. Third, core fill material, such as crushed rock, is placed in the cores of the blocks and spaces between the blocks to encourage drainage and add mass to the wall structure. Fourth, succeeding courses of the blocks are placed in a “running bond” pattern such that each block is placed between the two blocks below it. This is done by placing the blocks so that the receiving cavities of the bottom of the block fit over the pins that have been placed in the units in the course below. As each course is placed, pins are placed in the blocks, the blocks are corefilled with drainage rock, and the area behind the course is backfilled and compacted until the wall reaches the desired height.
Many retaining wall systems described in the art include the use of reinforcing materials, also referred to as geogrids, geosynthetic reinforcement, or geogrid soil reinforcement. These terms sometimes are used interchangeably, and “geogrid” as used herein is intended as a generic term. Reinforcement materials may be inextensible, such as steel mesh, or extensible geosynthetic materials, such as mats and oriented polymeric materials. For example, flat polymeric sheets are used to form geogrids by forming holes in the sheets and then drawing them to orient the polymer and increase the modulus. Such polymeric materials include high density polyethylene (HDPE) and these materials form relatively stiff geogrids commercially available under the trade designation “TENSAR”.
While the HDPE materials are relatively stiff, a second type of geosynthetic material is composed of a mat typically formed from polyester fibers that are woven or knitted. These may comprise rectilinear polymer constructions characterized by large (e.g., 1 inch (2.5 cm) or greater) openings. In these open structure geogrids, polymeric strands are woven, knitted or “welded” (by means of adhesives and/or heat) together in a grid. Polymers used for making relatively flexible geogrids include polyester fibers. The polyester typically is coated, commonly using a polyvinyl chloride (PVC) or a latex topcoat. The coating may contain carbon black for ultraviolet (UV) stabilization. Some open structure geogrids comprise polyester yarn for the warp fibers and polypropylene as the fill fibers.
Another flexible reinforcing geosynthetic material is geo-textile fabric, i.e., woven or non-woven constructions without large openings. These fabrics typically comprise polymers and may be referred to as geofabrics. The geofabric can be laid between courses of blocks in a wall, and typically is tied into the wall and held there. When blocks are configured to have pin connectors, for example, a hole or slit is formed in the geofabric at the construction site and the geofabric is held on the blocks by fitting it over the pins.
In common use, the geogrid extends behind the retaining wall and ties into the earth behind the wall, thus creating a cohesive soil mass tied into the wall facing that resists overturning. Geogrids are either mechanically connected to a course of blocks or rely on the friction created by placing the geogrid layer between courses of blocks. When the mode of connection is friction alone, the geogrid is placed on top of a course of blocks, and then a succeeding layer of blocks is placed on top of the geogrid. When the connection is mechanical, after placement of a course of blocks to the desired height, geogrid is placed onto a course of blocks and held in place by means of pins in the block (which may have a primary function of aligning and holding blocks together) or by means of special connectors. Flexible geogrid is put under tension by pulling back and staking the geogrid behind the retaining wall. Backfill is placed and compacted over the geogrid. Construction of the wall continues and may include additional layers of geogrid.
Such systems have proven reliable in many wall applications. There are limits to their performance however, particularly at the upper portions of the wall, where the load of the blocks above the geogrids layer do not provide as much load on the connection, so that frictional forces are reduced. The use of frictional connections forces the wall designer and builder to use more and higher strength geogrids because connection strength limits the strength of the system, and this adds expense to the wall. Mechanical connectors and retaining mechanisms attempt to overcome this limitation by mechanically connecting the geogrids to the wall facing in a way that is not load dependent. The difficulty with this approach is that in order for such connectors and retaining mechanisms to provide high levels of efficient connection they must add considerable expense to the cost of using the geogrids reinforcement, and add complexity and expense to the installation process. Thus there are shortcomings to both approaches.
However, it is desirable to facilitate construction methods of retaining walls as well as to optimize the ease of construction and durability of the wall being built.
It would be desirable to produce a wall block and a wall from the wall block having a pinning system for interlocking blocks.
It would further be desirable for the pinning system to be used with soil reinforcement materials, such as a geogrid.
It would also be desirable to produce a wall block having a pinning system for interlocking blocks and a channel with a channel bar that could be used in combination with soil reinforcement materials, such as a geogrid that would secure the soil reinforcement material to the block.
It would also be desirable to produce a retaining wall from a wall block having a pinning system for interlocking blocks and a channel with a channel bar that could be used in combination with soil reinforcement materials, such as a geogrid, to secure the soil reinforcement material to the block and thus the wall itself to allow for greater stability and durability of the retaining wall.
It would be further desirable to produce a retaining wall from a wall block with a channel bar system that interconnects courses of block with pins.
It would further be desirable to produce a wall, such as a retaining wall, from a wall block with a pinning system and/or a channel bar system that allows for the creation of curved, circular and serpentine shaped walls.